跳至主要内容

Fixed: Why iPhone 7 No 4G Signal

If there is only 2G signal on your cell phone and no 4G signal, this means that there are some problems in the 4G signal parts. This happens only after your mobile phone is water damaged, and the water intake is in the 4G signal channel.


Open the iPhone 7 and remove the motherboard to observe under HDMI camera stereo microscope, but we can't observe any traces, so we are going to remove the 4G power amplifier chip.

Remove the TDDPA_RF 4G power amplifier chip and measure the resistance value of the pad with Fluke digital multimeter. We found that the value of 11 pin MLB_PA_VBATT is infinitely large to the ground, it seems that the part is broken. As shown in picture 17-9-1.


Connect WUXINJI dongle and check the circuit diagram on computer, we can see some voltage go to TDDPA_RF and MLBPA_RF2 chips, and the MLBPA_RF chip was not installed.

The voltage is PP_PA_VBATT, which is renamed to MLB_PA_VBATT by R7113_RF resistor. The R7113_RF resistance has been corroded under microscope, as shown in picture 17-9-2.


The circuit icon is identified as 0 ohm resistance, so we short connect directly.

Once again testing iPhone 7 4G signal has returned to normal, water damage causes 4G power amplifier power supply is insufficient, so no 4G signal problem caused.

Repair is over here! More iPhone repair information please check on www.vipfixphone.com
标签：

评论

发表评论

此博客中的热门博文

iPhone 6 Display Failure after Replacing LCD

The iPhone 6 display is black after replacing LCD. After checking, the diode data of display socket is normal and all power supply for iPhone display IC  output is normal. Testing by  DC power supply , we find the iPhone current is abnormal. When press the iPhone power button, the boot current is obviously large. The current reached 100mA when press the power button. After remove the display tube, the current still the same, which means there is a short circuit. Measure the voltage output of each circuit of power supply with Fluke 15B+ Digital Multimeter , then surprised to find that there are really short circuit places. LD010 is short circuit; we suspect that the filter capacitance on the circuit has been penetrated. After remove the iPhone power control IC , we found it is ground short circuit. Open the WUXINJI Dongle  to check the iPhone schematic circuit, we found that this circuit is the display card image transmission MIPI data bus power supply. CPU brea...
发表评论
阅读全文

Solution: Why iPhone X Voltage Keeps Jumping

After getting the iPhone X motherboard to test, we observe the current value repeatedly jumps between 0mA and 50mA on DC power supply , and it is different from the normal booting current. Next, test whether the power supply of every circuit is normal. PP_VDD_MAIN is measured 4.2V; PP_VDD_BOOST measured is 4.2V. PP1V8-ALWAYS is 1.8V, all the values are normal. But when testing PP1V1_S2, PP0V8_SOC_FIXED_S1, PP1V8_S2 and other circuit voltage that output by power chip U2700 voltage are jumping constantly. According to previous experience, voltage jump is usually caused by a power supply circuit of U2700 output. Measured with digital multimeter , there is no short circuit was found for the dipole value of all power supply to ground. We repaired iPhone 7P before and know that if crystal oscillator is false welding can also cause voltage jumping, And if iPhone CPU  power supply is abnormal also can cause voltage jumping. Check the crystal oscillator we find no problem, then check th...
发表评论
阅读全文

Tutorial: iPhone 6S Plus Backlight Repair

Since the size of iPhone6s plus screen display  is large, it's necessary to use two sets of background lights to supply power, one is provided by U4020, the other is provided by U4050. 2  sets of circuit 1) PP_LCM_BL_ANODE,     PP_LCM_CAT1, PP_LCM_BL_CAT2 2) PP_LCM_BL34_ANODE,  PP_LCM_BL_CAT3, PP_LCM_BL_CAT4 For PP_LCM_BL_ANODE and PP_LCM_BL34_ANODE, if one of the circuit has no voltage value, it will cause the iPhone 6s Plus screen to be half bright and half dark. For PP_LCM_CAT1, PP_LCM_BL_CAT2, PP_LCM_BL_CAT3 and PP_LCM_BL_CAT4, if one of  these four circuits gets abnormal signal, it will cause the 1/4 screen to be dark. Solution: Use jumper wire  to short connect PP_LCM_CAT1 and PP_LCM_BL_CAT2 or you can also connect PP_LCM_CAT3 and PP_LCM_BL_CAT4. The control signals of these two sets of backlights, one group of inductors FL4211 FL4212 FL4213 are sent to the display interface. The other group is sent to the display interface...
1 条评论
阅读全文